Electroionic commutation system and its application, especially to the scanning in television



2,474,338 ELECTROIONIC COMMUTATION SYSTEM AND ITS APPLICATION,

June 28, 1949. P. M. G. TOULON ESPECIALLY TO THE SCANNING IN TELEVISION 3 Sheets-Sheet 1 Filed Aug. 4, 1947 TMI MM' v 5 5 E m n? a l 9 I N V EN TOR. PIERRE Map/s JFBPIE'L 751/: cu

4 TTORNEXS P. M. G. TOULON June 28, 1949. 2,474,338 ELEGTROIONIC COMMUTATION SYSTEM AND ITS APPLICATION,

ESPECIALLY TO THE SCANNING IN TELEVISION Filed Aug. 4, 1947 3 Sheets-Sheet 2 INVENTOR. P/ERRE 4/4/2/5 4452/5; 7504a June 28, 1949. P. M. G. TO ULON ELECTROIQNIC COMMUTATION SYSTEM AND ITS APPLICATION,

ESPECIALLY To THE SCANNING IFN TELEVISION I N V EN T 0R. H5225 MQ/P/E 6252/54 7'00: m

Patented June 28, 1949 UNITED STAT PATE. T 2,474,338

ELECTROIONIC COMMUTA'II-ON SYSTEM AND ITS APPLICATION, ESPECIALLY TO THE SCANNING IN TELEVISION Pierre Marie, Gabriel Toulon, Paris, France Claims.

My invention relates toa new process, intended for commutating an electric current of small intensity between two or several paths. In particular it can be used for bringing, at a given moment, two conductors to slightly different potentials. If the potential of one of said conductors varies in the courseof time and i i the other conductor is connected with a measuring instrument, assimilable to a low leakage capacity (for instance an electrometer), it becomes possible to record and approximately know the potential of the first conductor at a predetermined time.

The process can in particular be applied to the supply of the independent elements composing a large multi+element television screen of the type described in U. S. Patent No. 2,201,066, May 14, 1940 in my name. Each of its elements isrealised so as to transform into visual impulses the electrical video impulses which are applied thereto in the form of electro-static charges. Each one of the said electro-opticalelements (which in itself represents one of the points of the screen) is supplied with the electrostatic tension needed for its working.

I have already described in the above patent (as well asmy application Serial Number 213289, filed on November 6, 1938) (now Patent No. 2,471,253, dated May 24., 1949 the processes of distribution according to which the electrooptical elements disposed on a common. vertical line receive their modulation from potential. differences supplied by one common vertical conductor, the tension of which varies rather quickly in the course of time (forinstance 10,000ftimes per second if the screen comprises 400 horizontal lines explored 25 times per second) My present invention offers new and" practical means of realising the vertical distribution, i. e. of supply,- ing each one of the elements disposed on the same vertical line with tensions which correspond to the values of the potential of the said conductor in the course of time; in other terms, the means of commutating the elements disposed the one under the others. To that aim my invention makes use of the characteristics of the slow electrical discharge in the air (i. e. the glow' discharge); preferably obtained from an electrode causing in. its vicinity an intense condensation of the electric field (the said electrode having for instance the shape ofv a point or a needle).

The open air discharge in the neighbourhood of the needle is'in the form of. 'a corona containing electrified particles. This point is placed opposite two or several conductors, in a symmetrical way,and thelneedle is carried use high tension part of a is e screen.

2. with ieierence to the cc-ductors (for instance 5000 v'.)'.

I have observed that those conditions the glow dischargeeurrerit issumg from the nee'dle can be ans-cred: towards one or the other of the collecting electrodes opposite, according to the respective potentials of the said electrodes. The process of commutation der consideration, which lets the current pass? one direction only fiefiiect of a glow discharge diode), can be of advantage When a capacityintist he charged: and maintained charged for some time, and must afterwards bettischarged. a result may be obtained front a distance through a judicious choice of the; successive potentials applied to the electrodes the course of time. The voltages appliedsuccessively, according to my invention, to the collecting plates? result in directing towards the one or the other, of these latter the flux of positive or negativ'echarges, and in realising, from a distance, a sort of a local commutation without the help of any mechanical. device or any relay, and the said commutation is entirely automatic,

Of particular interest is that commutation at a distance for the supply of the independent elements ot a receiving television screen of the multi-element type, as will be more clearly understood by reierringto the following description andto the appended drawings (Figs. 1- to 5).

The said drawings, together with the following data relative to instances of application of my invention,- will be hell fulv tor a better understanding of its; object'and': itsforms of realisation, and shoulgdbe ih terpr eted in anon-limitative way.

Fig. 1 illustrates. the phenomena used in my inventionlarid the principles of the commutati'o n. drawn therefrom. e 1

Fig. 2 represents a diagram showing how-that commutationapplies to the control of the electro-optical elements of a large size screen television receiver.

Fig. 3 is av detail representation permitting a better understanding ofthe di-agramoi connections of Fig. 2'.-

Fig. 4a shows av front View and 4b across sectional View along XX of Fig'Aa, both referringto details of a form of execution of commutators intended; for being incorporated a largescreen.

Fig. 5 shows afiotlierforfi'i of realisation of the collecting electrode of a commutator forming a Fig.1, a needle stapes electrode is set semen war: to the two electrodes 1. 2 and r a'disnossd atavery short distance on from the other and generally plane. The electrodes 2 and 3 will, in the following description, be designated by the term collector. A commutator 6 permits to apply to the needle I either a high positive voltage 5, or a high negative tension 4 (with reference to the electrodes 2 and 3).

For the sake of clarity, I will assume that the point of connection of the batteries 4 and 5 is grounded at E. The potential of the collecting electrode 3 with reference to the ground, (which is included in the input circuit) can be modified in a variable manner in the course of time. I have assumed that the said variation was produced by means of a battery 9 and a commutator S which faces the contacts 9a9d. The electrode 2 is completely insulated and is grounded through a capacity I: the said electrode 2, together with its capacity, constitutes the output circuit. It will appear that the input and output circuits have a common point in E.

A characteristic feature of the needle is that it emits a flow of negative electric charges when it is connected to the battery 4, and a flow of positive charges when connected to the battery 5. I have observed that the flow of electric particles divides between the collecting electrodes 2 and 3 when they are at equal potentials. On the contrary, a very small difference between their potentials (for instance a few volts) is sufiicient for enabling one of the electrodes to practically collect the whole of the current while the other absorbs practically no current. If the needle is assumed to be negative, it is sufiicient that the electrode 2 be slightly negative with regard to the electrode 3 for observing that no negative charge falls on that electrode 2, and the whole of the current is concentrated on 3. On the contrary, if the needle is positive, a small positivity of the electrode 2 with regard to the electrode 3 is sufiicient for preventing the glow discharges to reach the electrode 2. Under those conditions, when the needle is negative, the collector 2 preserves its potential if initially negative, and if the initial potential of the electrode was positive, it is observed to vary, due to the absorption of the glow discharges, so that it adjusts itself to a value slightly negative but very nearly equal to the potential of the collector 3. On the contrary, when the needle is positive, if initially the potential of the electrode 2 was positive with regard to the electrode 3, no change can be observed; if contrarily the electrode 2 was initially negative, the potential of the electrode 2 adjusts itself to a value which is slightly positive but differs very little from the potential of the electrode 3. Thus by exercising a proper control on the commutators 6 and 8 it is possible to change, in one direction or in the opposite, the potential of the electrode 2.

The diagram under consideration (Fig. 1) permits to transmit across the condenser 1 a control voltage which is introduced between the collector 3 and the ground in the input circuit. The said control voltage is adjusted by means of the row of contacts of the battery 9. When the commutator 6 cuts in the battery 4, both plate electrodes are rendered positive with reference to the needle. The negative glow discharges reach both plates and they charge negatively the condenser I.

The discharges cut off automatically on the plate 2 when, as above said, its potential becomes negative by a few volts with reference to the potential of the plate 3. The charge thus imprisoned on the condenser will determine, at its terminals a voltage which will thus be nearly equal to the one introduced by the commutator 8, difi'ering by a small amount which is always the same (and has been observed by me as equal to 10 volts). When this charge is complete, the glow discharges are automatically transferred from collector 2 to collector 3, the co1lector 2 being thus insulated from that moment on; the collector 3 may be directly grounded without any charge resulting therefrom in the potential of the condenser, its charge being thus imprisoned. For discharging the condenser, the battery 5 is introduced by means of the commutator 6, with the result that the plate 2, which has been negative with reference to the plate 3, will draw towards itself the emission which is positive (ionic) for the present time: the plate 2 will thus absorb the said current till its potential again becomes equal, save that same small difference, to the potential of the plate 3.

In Figs. 2 and 3, the commutator 8 and the battery 9 have been replaced by a device introducing the television signals.

Fig. 2 illustrates the application of that imprisoning of charges to the control of the electrooptical elements composing a television screen. That control is operated from a television signal transmitted at a distance.

Fig. 3 shows a few components of the above said screen and it comprises all the circuits of a television receiving installation including the scanning necessary for operating the screen, and it will permit a better understanding of the working of the invention. In those figures (2 and 3) the same devices are designated by the same respective numbers.

I have, in Fig. 3, which shows the screen supply circuits and its elements in perspective, assumed that the surface of the said screen includes only 4 vertical lines corresponding to the conductors I9, I9, I9", I9, and 3 horizontal lines corresponding to the conductors 25, 26' and 26". An electro-optical element is shown in II, the energy consumption of which is practically negligible. To each one of the circuits of Fig. 3 must be supplied a voltage corresponding to the signals transmitted, in succession, through the common channel used for the television. For the sake of clarity the classical elements for the scanning of a multielement television screen have been recalled in the figure. The short waves received by the radio receiver I2 are selected, amplified and detected according to classical methods.

By means of an apparatus I3 the video impulses are extracted through the channel I4; the synchronising impulses for the line of pictures are received through the channel I5 and the image synchronising impulses are received through the channel I6. The line synchronising impulses serve to effect, by means of an appropriate device 20 operating at a high speed the distribution of the video impulses coming through the common channel I4, between a great number of conductors I9, I9, I9", I9', etc. This distributing device 20 is preferably realised in the form of a static type according to my prior application Serial No. 213,289 filed on November 6, 1938, in my name, and comprises namely a generator I7 of sensibilizing impulses displaced in time.

The modulation is imprisoned in each one of the conductors I9, during the time of transmission of one entire line. In the case of images corresponding to 400 lines of 500 points scanned 25 times per second, the number of incoming impulses received by each vertical conductor i9 amounts to 10,000 .per second. The image impulses (channel i6) are used for synchronising two small synchronous motors 16', I6". The needle 2i oi the above described commutator is set opposite to the 2 collectors l8 and I9. All the collecting electrodes I9 of each vertical line are stamped out of a common metallic band.

The potential of the collector is modified in the course of time according to a predetermined scanning cycle. The electrode 18 is connected to the condenser II, which is a component of the electro-optical element. The image point thus realised can diffuse or reflect an amount of light which is a function of the mean potential of that electrode l8.

The same electrode 1 8 is also connected, through a condenser 28, with an horizontal conductor 26. The said conductor is connected to one of the contacts of the rotary commutator 30.

The rotating brush 29, driven by the motor I6" is, connected with the brush 29 and serves to change abruptly during a very short time, the potential of the said conductor 26, by carrying it to the potential of the battery 21. By means of the capacity 28 which secures that connection, the instantaneous change in potential is transferred to the electrode I 8.

The needle 2| is also connected with another rotary commutator 30. On this second commutator successively contact two brushes, 22 and 23; the brush 23', connected with the battery 25, is effective to apply to the point 2| 2. high positive voltage during a short time interval, while the brush 22, connected with the battery 24, is afterwards efiective to apply to the needle 2| a high negative voltage, also for a short duration.

All the other collecting electrodes l8, I8", 18'' of the other elements of the horizontal line to which belong the collector 18 are similarly, by the condensers '28, 28", 28" connected in parallel, on the conductor 26. The electro-optical elements have been omitted in the figures. The other horizontal lines 26 and 26" are similarly connected with other collecting electrodes and other screen elements, not shown in the figure. Opposite all the other electrodes, corresponding needles are installed, and all the needles belo ing to an horizontal row are connected in parallel.

The system works as follows:

At a certain moment, the various conductors l9, l9, l9" share in a distribution of potentials which respectively correspond to the tint of the various points of an horizontal line of the televised image. The problem is to transmit to the electrodes I8, l8, l8", supplying the various electr'o-optical elements the corresponding tensions, i. e. to record the actual distribution of tensions. That result is obtained by the used of the phenomenon illustrated by theFig. 1. Prior to the moment of the recording, the needles 2| have been carried by the brushes :22 to a high negative tension.

As the condensers 28, 28', 28" are charged slightly negatively (as explained above with reference .togi-g. 1) the whole output of the glow discharge is normally absorbed by the electrodes l9, l9, l9", l9, which are at a. higher positive voltage than the electrodes 18, l8, I8", 18".

Normally the band 26 is grounded through ahigh resistance R shunted by a condenser. The junction point of the batteries 24, 25 is also grounded. The potential of the other band is similarly determined.

At the precise moment of the recording, a momentary contact 29-30 suddenly charges the capacity C in parallel with the resistance R, thus increasing by an exactly known amount the potential of the conductor 26. That variation of the tension has a repercussion on the plates l8, 18', I8" which become momentarily more positive. That is effective to displace the output of the glow discharge towards those electrodes [8. The said electrodes cease automatically to deliver current when their potential distribution, at the time under consideration, exactly corresponds to the voltage distribution of cooperative collectors belonging to the vertical conductors l9, I9, I9", 19", i. e. to the distribution of video signals already imparted to the last bands. As soon as the impulses given by the brush 29 has ceased on the conductor 26 (its duration being of the order of /1o.ooo of a second in the case above considered), that conductor returns to ground potential.

As the electrodes 18, l8, l8" have acquired during this period of sensibilisation a negative potential with regard to the corresponding collectors 19 to 19", and consequently are no longer in contact with the glow discharges, their respective condensers 28 to 28" keep the charges they had acquired, and the duration of the retained charges is equal to the duration of the exploration of one image. The electro-optical elements ll connected with the said condensers are thus modulated by the video signals and reproduce the image of one horizontal line of the picture.

It can therefore be said that the instantaneous potential of the conductor l9 (1. e. tiaooo of a second corresponding to the exploration of an horizontal line) keeps recorded on the conductor l8 during of one second (i. e. the duration of the exploration of one image). Such a recording can be realised simultaneously by a large number of elements I8, [8, 18" corresponding only to an important fraction (for instance one quarter) of the length of the line.

During the next interval of time after sensibilization of line 26 ($5 of a second), the recording is realised on the elements of the following horizontal line, connected with the horizontal conductor 26'. That operation is thus repeated, in succession, on each one of the lines as fast as the brush 29 rotates on the commutator 3B (and the brushes 22 and 23 follow the same cadence).

At the end of the duration of one scanning of the image, and before realising a new recording, it is necessary to drain out the negative charges respectively imprisoned in the condensers 28: a result which is obtained from the fact that the brush 23 momentarily carries the needle to a high positive tension, which carries the glow discharge to 8 and neutralizes the negative charges imprisoned in their condensers.

The stoking and the evacuation of the impulses isv thus realised for each one of the elements respectively, at the proper time; a result which is secured automatically by means of entirely static devices, of very little dimensions and cost, and all disposed within the screen.

According to a form of realisation of the above described commutator it is of advantage to give the collectors the shape of two conductors of very small section, with a high insulation, set in very close proximity as illustrated in Fig. 4. The process of execution may be as shown in Fig. 4. In a thin rhodoid band 38, for instance, are seen as many holes as the apparatus must have needles, these holes 41 being so positioned as to correspond to the positions of the needles 2|. In the same band are seen a number of slots 48 and 49. The collecting electrodes belonging to the same vertical lines are realised in the form of a very fine vertical wire 4|, which is fixed in the slots 48 The insulated collectors are similarly composed of one wire 42, which is fixed in the slots 49 and in the interval of the groups of slots is left a loop 44 of this wire 42, which loop will be subsequently divided up into sections. The sheet 38 is coated, as seen in section Fig. 4b, with a thin sheet 36, carrying holes registering with the holes at, which sheet 36 is pasted to the sheet 33. Thus are immobilised the wires 4| and 42, with a very small space between them. After having made in this way several bands 38 one may paste thereon perpendicular bands (not shown in this figure, and corresponding to the bands 26 of the Figure 3). Each one of the last bands forms one armature of the coupling condenser 28 of the last figure, and the second armature is formed by the section of the wires 42.

Fig. 5 illustrates another form of execution of the collectors, intended for being incorporated in a large screen. The band 54 represents one of the collectors grouped in the same vertical line and '54 the associated collectors of the same line. Both devices are shaped in the form indicated and are realised by coating a common support 53 with a sheet of conducting material.

What I claim is:

1. An electro-ionic commutator comprising a glow discharge electrode, first and second collecting electrodes symmetrically disposed with respect to said glow discharge electrode, means for introducing relatively controllable potentials between each of said first and second collecting electrodes and said glow discharge electrode, the magnitude of at least one of said potentials being sufiicient to effect glow discharge selectively from said glow discharge electrode to only one of said collecting electrodes.

2. A system for charging a condenser to a potential determined by a control voltage, comprising, an electro-ionic device having a glow discharge electrode and first and second collecting electrodes disposed co-planarly and symmetrically with respect to said glow discharge electrode, means for connecting one terminal of said condenser to said first collecting electrode and the remaining terminal of said condenser to a point maintained at reference potential, means for applying a controllable potential between said second collecting electrode and said point, means for applying a further controllable potential between said glow discharge electrode and said point, the potential between at least one of said collecting electrodes and said pointed electrode having sulficient magnitude to effect glow discharge from said glow discharge electrode.

3. A system for charging and. discharging a condenser, comprising, an electro-ionic device having a glow discharge electrode and first and second collecting electrodes disposed symmetrically with respect to said glow discharge electrode, means connecting said condenser between said first collecting electrode and said glow discharge electrode in series with a source of voltage, means for connecting said second collecting electrode to said glow discharge electrode via an adjustable and reversible source of voltage, and means for varying the voltage between said second collectin electrode and said glow discharge electrode selectively to values reater and less than voltage existing between said glow discharge electrode and said first collecting electrode.

4. The combination in accordance with the preceding claim wherein is further provided means for reversing the polarity of the voltage between said second collecting electrode and said glow discharge electrode.

5. In combination, in an electro-ionic commutator, a glow discharge electrode and a first and second collecting electrode, a condenser connected between said first collecting electrode and a point of reference potential, means for applying a variable voltage between said second collecting electrode and said point, and means for applying a reversible voltage between said point and said glow discharge electrode, of sufiicient magnitude to effect glow discharge between said glow and one of said collector electrodes selectively in accordance with the relative potentials of said collector electrodes with respect to said point.

6. An electro-ionic commutator comprising, a glow discharge electrode, first and second collecting, electrodes symmetrically disposed with respect to said glow discharge electrode, means for introducing relatively controllable potentials between each of said first and second collecting electrodes and said glow discharge electrode, the magnitude of at least one of said potentials being sufiicient to efiect glow discharge selectively from said glow discharge electrode to only one of said collective electrodes, said glow discharge electrode comprising a sharply pointed electrically conducting element extending in a first direction in space, and said first and second collecting electrodes each comprising an electrically conducting plate, said plates arranged in a common plane oriented perpendicularly to said first direction, said plates being mutually insulated.

7. A system for charging a condenser to a potential determined by a control voltage, comprising, an electro-ionic device havin a glow discharge electrode and first and second collecting electrodes disposed co-planarly and symmetrically with respect to said glow discharge electrode, means for connecting one terminal of said condenser to said first collecting electrode and the remaining terminal of said condenser to a point maintained at reference potential, means for applying a controllable potential between said second collecting electrode and said point, means for applying a further controllable potential between said glow discharge electrode and said point, the potential between at least one of said collecting electrodes and said pointed electrode having sufficient magnitude to eifect glow discharge from said glow discharge electrode, said glow discharge electrode comprising a sharply pointed electrically conducting element extending in a first direction in space, and said first and second collecting electrodes each;. comprising an electrically conducting plate, said plates arranged in a common plane oriented perpendicularly to said first direction, said plates being mutually insulated.

8. A system for charging and discharging a condenser, comprising, an electro-ionic device having a glow discharge electrode and first and second collecting electrodes disposed symmetri-- cally with respect to said glow 'discharge electrode, means connecting said condenser between said first collecting electrode and said glow dis-- charge electrode in series with a source of voltage, means for connecting; said second collecting electrode to said glow discharge electrode via an adjustable and reversible s cc of voltage,

U and. means for varying the voltage between said second collecting electrode and said glow discharge electrode selectively to values greater and less than the voltage existing between said glow discharge electrode and said first collecting electrode, said glow discharge electrode comprising a sharply pointed electrically conducting element extending in a first direction in space, and said first and second collecting electrodes each comprising an electrically conducting plate, said plates arranged in a common plane oriented perpendicularly to said first direction, said plates being mutually insulated.

9. The combination in accordance with the preceding claim wherein is further provided means for reversing the polarity of the voltage between said second collecting electrode and said glow discharge electrode.

10. In combination, in an electro-ionic commutator, a glow discharge electrode and a first and second collecting electrode, a condenser connected between said first collecting electrode and a point of reference potential, means for applying a variable voltage between said second c01- lecting electrode and said point, and means for applying a reversible voltage between said point and said glow discharge electrode, of sufiicient REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,179,105 Sidney l {ov. 7, 1930 2,231,877 Bennett Feb. 18, 1941 FOREIGN PATENTS Number Country Date 48,904 France Sept. 21, 1938 860,481 France Jan. 16, 1941 

